Spatially and temporally resolved optical measurements in micro discharges

Optical measurements provide a convenient way to determine plasma properties such as particle densities and temperatures. Since optical measurements are usually conducted externally, they give only little information about the spatial distribution of the plasma. This is especially egregious when dealing with micro discharges. Firstly, micro discharges usually show a spatial non-uniformity, and secondly, the small dimensions oppose the feasibility of many diagnostics which provide spatially resolved information. We present a new technique for spatially resolved optical measurements in micro discharges by using an optical fibre as probe. The feasibility of this technique is demonstrated by measurements on a micro thin-cathode discharge. This discharge has dimensions smaller than 100 micrometres and exhibits plasma densities of up to 10 cm. We also provide measurements of the gas temperature and emission spectrum of the discharge.